High Yield Imaging

Biodistribution Atlas

Whole-body bone scan (Tc-99m MDP), anterior and posterior views, labelled: bladder, knee joint, spine, kidney. Handwritten note: dark = more tracer.
Bone scan: Obeng F, Yawson A, Hammond NB, et al. Cureus 2025, Fig. 3, CC BY 4.0, doi:10.7759/cureus.87786. Cropped; labels added.

Biodistribution Atlas

Before you can call a lesion, you have to know where a tracer belongs. This atlas maps the normal physiological uptake and the common variants for the tracers you’ll read most, so that physiology is not mistaken for pathology.

Updated September 2026 · 5 sources listed

On this pagePET tracersSPECT tracersNeuro & endocrineUse it with the rest of the siteSources
Always correlate with hybrid CT/MR and the clinical picture.

PET tracers

F-18 FDG

Normal high uptake

Brain (grey matter), myocardium (variable), liver + spleen background, renal collecting system + bladder (excretion), Waldeyer’s ring / tonsils, bowel (variable).

Variants

  • Brown fat (neck, supraclavicular, paraspinal): symmetric, follows fat on CT.
  • Muscle uptake (talking, tension, insulin).
  • Ovaries (ovulation), endometrium (menses); testes low-level.
  • Thymus in children (inverted-V).

Pitfalls

  • Bowel + marrow (post-G-CSF) can mask/mimic disease; keep patient warm/rested to suppress brown fat + muscle.

Ga-68 PSMA

Normal high uptake

Lacrimal + salivary glands, liver, spleen, kidneys + urinary tract (excretion), small bowel/duodenum, coeliac ganglia (can mimic node).

Pitfalls

  • Ureteric activity mimics nodes; furosemide + delayed pelvic view.
  • Coeliac/stellate ganglia + healing bone (fracture, Paget) can be PSMA-avid; read with CT.

Ga-68 DOTATATE (SSTR)

Normal high uptake

Spleen (highest), then adrenals, kidneys, liver, pituitary, salivary glands, thyroid; uncinate process of pancreas (variant).

Pitfalls

  • Uncinate pancreatic uptake mimics a NET; know the variant.
  • Accessory spleen/splenosis; inflammation can express SSTR.

F-18 NaF (bone PET)

Normal uptake

Skeleton throughout (high bone-to-background), growth plates in children, renal excretion + bladder.

Pitfalls

  • Degenerative + benign lesions are also fluoride-avid; correlate CT as with MDP.

SPECT tracers

Tc-99m MDP (bone)

Normal uptake

Symmetric skeleton, kidneys + bladder (excretion), faint soft tissue on delayed. Growth plates + sternum variable.

Variants / pitfalls

  • Kidneys are normally faintly visible; faint or absent kidneys with intense skeletal uptake suggest a superscan.
  • Free pertechnetate → thyroid/stomach/salivary uptake (poor tag).
  • Urine contamination mimics lesions; breast/attenuation shadows.

Tc-99m MAG3 / DMSA (renal)

Normal uptake

MAG3: prompt symmetric renal cortical uptake → pelvicalyceal → bladder; some hepatobiliary if impaired. DMSA: cortical binding, ~50:50 split.

Pitfalls

  • Full bladder/dehydration distorts drainage curves; column-of-Bertin variant on DMSA.

Tc-99m MAA (lung perfusion)

Normal uptake

Homogeneous perfusion filling both lungs. MAA is injected supine, which minimises the gravitational apex-to-base gradient seen with upright injection.

Pitfalls

  • Clumped MAA = focal hot spots (technique); free Tc → thyroid/kidney; shunt → systemic (brain/kidney) uptake.

Neuro & endocrine

I-123 ioflupane (DaTscan)

Normal uptake

Symmetric comma/crescent-shaped striatal uptake (caudate + putamen), low background elsewhere.

Abnormal

  • Reduced putaminal uptake → “period/full-stop” shape = presynaptic dopaminergic loss.
  • Ensure thyroid block; scalp/skull background if poor block.
Two real DaTscan slices at the striatum. Normal, left: labelled comma shape and putamen. Parkinson’s disease, right: labelled caudate and full stop shape. Handwritten note: in Parkinson’s disease, loss is first seen in the posterior putamen, opposite the more affected side.
Real DaTscan slices: the normal comma shape (left) and the full-stop shape of Parkinson’s disease (right). Compare the shapes, not the colours: each scan has its own colour scale. Normal: Sasaki 2021, Front Neurol, Fig. 2, CC BY, doi:10.3389/fneur.2021.656679. Parkinson’s disease: Balcerzak et al. 2025, Cureus, Fig. 1A, CC BY 4.0, doi:10.7759/cureus.88177. Cropped; labels added.

Thyroid (Tc-99m pertechnetate / I-123)

Normal uptake

Homogeneous butterfly (two lobes + isthmus), ± pyramidal lobe variant; salivary glands + gastric mucosa with pertechnetate.

Pitfalls

  • Recent iodine (contrast/amiodarone) blocks uptake; discordant nodule between Tc and I-123.

I-123 mIBG

Normal uptake

Myocardium, liver, spleen, salivary glands, bowel, bladder; adrenals faint (variable).

Abnormal / pitfalls

  • Focal uptake = phaeo/paraganglioma or neuroblastoma. Thyroid block essential; interfering drugs reduce uptake (false negative).

Use it with the rest of the site

Match normal here to the study set-up in the Explorer and the tracer physiology in the Radiopharmaceutical Reference; separate variant from disease with the DDx Guide and mimics with the Artifact Atlas.

Sources

  1. SNMMI / EANM procedure guidelines (normal biodistribution + variants per tracer). eanm.org
  2. PROMISE / normal PSMA biodistribution; DOTATATE physiological uptake references. J Nucl Med.
  3. Ziessman et al., Nuclear Medicine: The Requisites (normal variants).
  4. Parker JA, Coleman RE, Grady E, et al. SNM practice guideline for lung scintigraphy 4.0. J Nucl Med Technol. 2012;40(1):57–65. doi.org/10.2967/jnmt.111.101386
  5. Bajc M, Schümichen C, Grüning T, et al. EANM guideline for ventilation/perfusion single-photon emission computed tomography (SPECT) for diagnosis of pulmonary embolism and beyond. Eur J Nucl Med Mol Imaging. 2019;46(12):2429–2451. doi.org/10.1007/s00259-019-04450-0

High Yield Imaging · Normal Biodistribution Atlas. Correlate with hybrid imaging + clinical context.

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Educational reference for imaging professionals. It does not replace local policy, manufacturer labelling or clinical judgement.

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